Method and system for handling a dynamic host configuration protocol internet protocol version 4 address release

ABSTRACT

A method and system for releasing an Internet Protocol (IP) version 4 address using a Dynamic Host Configuration Protocol (DHCP) release in a Proxy Mobile IP version 6 (PMIPv6) of a third Generation Partnership Project (3GPP) Evolved Packet Core (EPC). The method includes transmitting a DHCP release request from a Serving GateWay (SGW) to a Packet Data Network (PDN) GW, transmitting a binding revocation from the PDN GW to the SGW, acknowledging the binding revocation from the SGW to the PDN GW, and deleting the IP version 4 connection for an active PDN connection.

PRIORITY

This application claims priority under 35 U.S.C. §119(a) to applicationsfiled in the Intellectual Property Office of India on Aug. 14, 2008 andJul. 31, 2009, which are assigned Indian Priority Document No.1985/CHE/2008 and 1985/CHE/2008, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates generally to a field of a ThirdGeneration Partnership Project (3GPP) Evolved Packet Core (EPC) and moreparticularly, to a method and a system for handling a Dynamic HostConfiguration Protocol (DHCP) Internet Protocol version 4 (IPv4) addressrelease request with a Proxy Mobile Internet Protocol (PMIP) or aGeneral Packet Radio Service (GPRS) Tunneling Protocol (GTP) basednetwork.

2. Description of the Related Art

The 3GPP EPC supports two types of protocol over an S5 or S8 interface.Here the S5 will have a context of a User Equipment (UE) residing in ahome operator and the S8 will have another context of the UE roamingwith a visited operator. The two types of protocols include GTP andPMIP. The UE behavior is independent of the protocol. The UE has a Layer2 (L2) connection with a Serving GateWay (SGW). The S5 or S8 connectioncan be for GTP or PMIP.

In a GTP based S5 or S8 connection, a GTP tunnel is formed between anSGW and a Packet Data Network (PDN) GW. For a PMIP based an S5 or S8connection, a PMIP tunnel is formed between the UE and PDN GW.

In the existing techniques, the PDN includes a connection relatedcontext in the UE, a Mobile Management Entity (MME), an SGW, and a PDNGW. The context may or may not include an IP address.

A PDN connection can be allocated to at least one of an IPv4 address andan IPv6 address. A Binding Revocation (BR) is used by the Local MobilityAnchor (LMA) to revoke a binding for a particular UE. Further, for thePDN connection utilizing the PMIP based S5 or S8, the IP address formsintegral part of the PMIP tunnel between the PDN GW and the SGW.According to the PMIP version 6 (PMIPv6), a Binding Cache Entry (BCE)and a Binding Update List (BUL) cannot be maintained without an IPaddress allocated for the UE. However in the existing techniques, thePDN connection may be lost when the IP address is deleted.

In light of the foregoing, there is a need for an efficient technique ofhandling a DHCP version 4 (IPv4) address release request with a PMIP orGTP based network.

SUMMARY OF THE INVENTION

The present invention has been made to address at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, embodiments of the present disclosuredescribed herein provide methods and systems for handling a DHCP IPv4address release request with a PMIP or GTP based network.

In accordance with an embodiment of the present invention a method isprovided for releasing an IPv4 address using a DHCP release in a PMIPv6of 3GPP EPC. The method includes transmitting a DHCP release requestfrom an SGW to a PDN GW, transmitting a BR or a PDN disconnection fromthe PDN GW to the SGW, acknowledging the BR from the SGW to the PDN GW,and deleting the IPv4 connection for an active PDN connection.

In accordance with another embodiment of the present invention a methodis provided for re-allocating an IPv4 address using a DHCP request,after an IP address is deleted by the DHCP release. The method includessending an IP address update request from an SGW to a PDN GW, receiving,by the SGW, an actual IP address acknowledgement from the PDN GW, andre-attaching the actual IP address by the SGW.

In accordance with another embodiment of the present invention a systemis provided for deleting a DHCP release in a PMIPv6 of a 3GPP EPC and aSGW. The SGW further includes a DHCP relay for transmitting a DHCPrelease request between the SGW and a PMIP Mobile Access Gateway (MAG).The system also includes a PDN GW including a DHCP server. The DHCPserver includes a local mobility anchor for revoking a binding for a UE.The system further includes a link between the SGW and the UE fortransmitting a DHCP release request. Further, the system includes aPMIPv6 or GPRS between the SGW and PDN GW server. The system alsoincludes a tunneled link between the SGW and the PDN GW for transmittingthe release request.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptionwhen taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a system for deleting a Dynamic Host ConfigurationProtocol (DHCP) release in a Proxy Mobile Internet Protocol version 6(PMIPv6) of a 3GPP Evolved Packet Core (EPC), in accordance with anembodiment of the present invention;

FIG. 2 is a flowchart illustrating a method for releasing an IP version4 address using a DHCP release in PMIPv6 of a 3GPP EPC, in accordancewith an embodiment of the present invention;

FIG. 3 is a flowchart illustrating a method for re-allocating IP version4 address using the DHCP version 4 request, after an IP address isdeleted by the DHCP release, in accordance with an embodiment of thepresent invention;

FIG. 4 is a flow diagram illustrating a method for deleting a connectionbetween a Serving GateWay (SGW) and a Packet Data Network GateWay (PDNGW), in accordance with an embodiment of the present invention;

FIG. 5 is a flow diagram illustrating a method for triggering a DHCPrelease, after the UE requests for an IP address, in accordance with anembodiment of the present invention;

FIG. 6 is a flow diagram illustrating a method for initiating a packetdata disconnection procedure for a PDN GW, in accordance with anembodiment of the present invention;

FIG. 7 is a flow diagram illustrating a method for retaining aconnection active between the SGW and a PDN GW, using a dummy IPaddress, in accordance with an embodiment of the present invention;

FIG. 8 is a flow diagram illustrating a method for re-attaching anactual IP address with the dummy IP address, in accordance with anembodiment of the present invention;

FIG. 9 is a flow diagram illustrating a method for deleting a PDNinitiated IP version 4 address, in accordance with an embodiment of thepresent invention; and

FIG. 10 is a flow diagram illustrating a method for deleting the SGWinitiated IP version 4 address, in accordance with an embodiment of thepresent invention.

In the accompanying figures, similar reference numerals may refer toidentical or functionally similar elements. These reference numerals areused in the detailed description to illustrate various embodiments andto explain various aspects and advantages of the present disclosure.

Further, persons skilled in the art will appreciate that elements in thefigures are illustrated for simplicity and clarity and may have not beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of various embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

It should be observed that various method steps and system componentshave been represented by conventional symbols in the figures, showingonly specific details that are relevant for an understanding of thepresent disclosure. Further, details that may be readily apparent to aperson ordinarily skilled in the art may not have been disclosed.Additionally, in the present disclosure, relational terms such as firstand second, source and target, etc., may be used to distinguish oneentity from another entity, without necessarily implying any actualrelationship or order between such entities.

Embodiments of the present disclosure described herein provide methodsand systems for handling a Dynamic Host Configuration Protocol (DHCP)Internet Protocol version 4 (IPv4) address release request with a ProxyMobile Internet Protocol (PMIP) or a General Packet Radio Service (GPRS)Tunneling Protocol (GTP) based network.

FIG. 1 illustrates a system for deleting a DHCP release in PMIPv6 of athird Generation Partnership Project (3GPP) Evolved Packet Core (EPC),in accordance with an embodiment of the present invention. Anenvironment 100 includes a User Equipment (UE) 105, such as a mobilephone, a computer, a camcorder, a television, and a Personal DigitalAssistant (PDA). A network 110 is connected to a Serving GateWay (SGW)115 and a PDN GW 125. The SGW further includes a DHCP relay 120, whichis used to transmit a DHCP release request between an UE and a PMIPv6LMA.

The PDN GW 125 includes a DHCP Server 130. Further, although notillustrated, the PDN GW 125 includes a Local Mobility Anchor (LMA) forrevoking a binding for a UE. A link exists between the SGW and the UEand a PMIPv6 tunnel exists between the SGW and PDN GW server to transmita DHCP release request

FIG. 2 is a flowchart illustrating a method for releasing an IPv4address using a DHCP release in a PMIPv6 of a 3GPP EPC, in accordancewith an embodiment of the present invention.

In step 205, the method is started by activating a PDN connectionbetween the UE and the SGW, and allocating the UE with an IPv4 address.The UE uses a DHCP for obtaining the IP address. A connection is alsoactivated between a SGW and a PDN GW.

In step 210, a DHCP release request is transmitted from the SGW to thePDN GW. The IP address allocated to the UE is released. The DHCP serverfurther triggers the IP address release procedure with an LMA functionassociated with PDN GW. The DHCP server receives the DHCP releasemessage, and the IP address allocated to the UE is released. The DHCPserver also triggers the IP address release procedure with the LMAfunction associated with PDN GW. The LMA includes an indication, e.g., abit or a flag in the PMIPv6 message, to the SGW. The LMA indicationindicates an initiation by the LMA not to delete the PDN connection.Accordingly, the above-described process will retain the PDN connectionas active. The PDN connection context is then deleted by the PDN GWkeeping the connection active in the SGW, a Mobile Management Entity(MME), and a UE.

In step 215, a Binding Revocation (BR) or a PDN disconnection istransmitted from the PDN GW to the SGW.

In accordance with an embodiment of the present invention, the BR istransmitted by allocating a dummy IP address to keep the PDN connectionactive.

In accordance with another embodiment of the present invention, a flagspecific to the IPv4 to be deleted is provided.

In step 220, a BR ACKnowledgement (ACK) is provided from the SGW to thePDN GW.

In step 225, the IPv4 connection for the active PDN connection isdeleted. The SGW deletes the connection after receiving the DHCP releaserequest and updates the PDN connection for deleting the IP addressconfiguration information.

In accordance with an embodiment of the present invention, deleting theIPv4 connection includes removing an actual IP address and updating adummy IP address from the PDN GW to the SGW to keep the PDN connectionactive.

In accordance with an embodiment of the present invention, the SGWinterprets the DHCP request and initiates the Proxy Binding Update (PBU)towards the PDN GW.

FIG. 3 is a flowchart illustrating a method for re-allocating an IPv4address using the DHCP version 4 request, after an IP address is deletedby the DHCP release, in accordance with an embodiment of the presentinvention.

In step 310, an IP address update request is sent from an SGW to a PDNGW. The SGW, which includes the PDN connection context with a dummy IPaddress, sends a PBU to the PDN GW with an indication to allocate a HomeAddress (HoA). As part of processing the PBU, the PDN GW allocates an IPaddress and replies with an actual IP Address.

In step 315, the PDN GW sends an actual IP address ACK to the SGW.

In step 320, the actual IP address is re-attached by the SGW, uponreceiving the IP address acknowledgement. The UE confirms the IP addressreceived from the DHCP server.

In accordance with an embodiment of the present invention, a PMIPv6between the SGW and the PDN GW may be deleted. If the UE requests anIPv4 address for the PDN connection, the PMIP tunnel is updated betweenthe SGW and the PDN GW.

FIG. 4 is a flow diagram illustrating a method for deleting a connectionbetween an SGW and a PDN gateway, in accordance with an embodiment ofthe present invention. In step 1, a PDN connection is activated for a UEby allocating an IPv4 address. The UE uses a DHCP to obtain the IPaddress and to configure one or more parameters in an IP stack. In step2, the UE initiates the DHCP release for releasing the IP address bysending a request for releasing the IP address to the SGW. The DHCPrelease request is relayed by the SGW, i.e., a DHCP relay, to the PDNGW. The PDN GW is located at the DHCP server. If the DHCP serverreceives the DHCP release request, the IP address allocated to the UEwill be released. The DHCP server triggers the IP address releaseprocedure with an LMA function associated with the PDN GW. In step 3, anLMA initiates a PMIP binding revocation procedure. The bindingrevocation procedure is used by the PDN GW for deleting the PDNconnection, and an indication is used to differentiate between thebinding revocation procedure and the PDN disconnection procedure. TheLMA indicates the SGW of the initiation of the binding revocationprocedure by the LMA in order to delete the S5 or S8 context for the PDNGW, while keeping the PDN connection active. For example, the S5 or S8connection only indication can be indicated by a bit or a flag in thePMIPv6 message. The SGW deletes the one of a S5 and S8 context, therebymaintaining the active PDN connection in the SGW, a Mobile ManagementEntity (MME), and the UE. The SGW receives a Binding RevocationIndication (BRI) and deletes the one of an S5 and S8, and then updatesthe PDN connection to delete the IP address configuration information.In step 4, the SGW sends a BR ACK to the PDN GW.

In accordance with an embodiment of the present invention, the SGW caninterpret the DHCP request and then initiate the PBU towards the PDN GW.

FIG. 5 is a flow diagram illustrating a method for triggering a DHCPrelease after a UE requests an IP address, in accordance with anembodiment of the present invention.

In step 1, the UE releases an IPv4 address for a PDN connectionallocated with the IPv4 address. That is, the UE performs a DHCP releaseprocedure. In step 2, the UE initiates a DHCP discover procedure toprocure an IPv4 address.

In step 3, the SGW includes the context related to the PDN connectionfor the UE and the DHCP discover message, which is a DHCP protocolmessage defined in DHCP RFC, is buffered by a DHCP relay included in theSGW. The SGW in turn initiates a PBU procedure to obtain an IP addressby sending a Proxy Binding Update (PBU) to the PDN GW. The PDN GWprocesses the PBU normally like a new PDN connection and allocates an IPaddress. The PBU is included in the PMIP Binding Acknowledgement (PBA)transmitted to the SGW.

In step 4, the DHCP relay in the SGW forwards the DHCP discover from theUE to the PDN GW.

In step 5, a DHCP offer is transmitted from the SGW to the UE. The DHCPoffer includes the IP address, which was allocated in the PBA.

In accordance with an embodiment of the present invention, the IPaddress can be the previously allocated IP address. In accordance withanother embodiment, a new IP address can be allocated.

In step 6, the UE confirms the IP address received from the DHCP serverin PDN GW by transmitting DHCP Request for the allocated IP address. TheDHCP transaction is complete by the DHCP Server Acknowledging the DHCPrequest.

FIG. 6 is a flow diagram illustrating a method for initiating a packetdata disconnection procedure for a PDN GW, in accordance with anembodiment of the present invention.

In step 1, a PDN connection is active for the UE. That is, the UE isallocated with an IPv4 address, and uses a DHCP for obtaining the IPaddress and for configuring one ore more parameters in an IP stack.

In Step 2, the UE decides to release the IP address. More specifically,because the UE has used the DHCP for configuring the IP address, the UEinitiates the DHCP release for releasing the IP address by transmittinga DHCP release request to the SGW. The DHCP release request is thenrelayed by a DHCP relay included in the SGW to the DHCP server.

In Step 3, after receiving the DHCP release request, the IP addressallocated to the UE is released by the PDN GW. The DHCP server triggersthe PDN GW and initiates a procedure for the PDN GW disconnectionprocedure. The procedure releases the PDN connection (S5 or S8) contextin the network and the UE.

In accordance with another embodiment of the present invention, the SGWmay interpret the DHCP request in step 2 and initiates the PDNdisconnection procedure towards the UE and towards the PDN GW.

FIG. 7 is a flow diagram illustrating a method for retaining an activeconnection between an SGW and a PDN GW, using a dummy IP address, inaccordance with an embodiment of the present invention.

An IP address allocated to a UE is used for tunneling between a MAG andan LMA. The S5 or S8 tunnel between MAG and LMA establishes the PDNconnection. Here, the S5 will have a context of a UE residing in thehome PLMN and the S8 will have another context of a UE roaming inVisited PLMN. The tunnel can be modified to provide a dummy IP addressin a Binding Cache Entry (BCE). The BCE includes a UE Network AccessIdentifier (NAI) and an Access Point Name (APN) for identifying the PDNconnection and to be identified in future for further transactions, suchas a PDN disconnect procedure or an IP address re-attach triggered by aUE initiated DHCP discover message.

In step 1, a PDN connection is active for the UE. That is, the UE isallocated an IPv4 address, and uses a DHCP for obtaining the IP addressand for configuring one or more parameters in an IP stack.

In step 2, the UE makes a decision to release the IP address andtransmits a DHCP release request to the SGW. The DHCP release request isrelayed by the DHCP relay included in the SGW to the PDN GW. Asillustrated in FIG. 5, the IP address allocated to the UE is released bythe PDN GW, after receiving the DHCP release request. More specifically,the DHCP server triggers the IP address release procedure with an LMAfunction associated with the PDN GW.

In step 3, the PDN GW sends an IP address update message to the SGW,including a dummy IP address, for example (0.0.0.0). The updated IPaddress message can be a binding revocation with an optional field forupdating a Binding Update List (BUL). The IP address message replaces aHoA allocated to the UE with a temporary IP address. The entry in theBUL indicates that the PDN connection is not related to any IP address.

In step 4, the SGW sends an IP address update ACK to the PDN GW.

In accordance with another embodiment of the present invention, the SGWcan interpret the DHCP request and can initiate an IP address updatemessage towards the PDN GW. Thereafter, DHCP release request is relayedby the DHCP relay included in the SGW to the PDN GW.

FIG. 8 is a flow diagram illustrating a method for re-attaching anactual IP address with a dummy IP address, in accordance with anembodiment of the present invention.

In step 1, a UE releases an IPv4 address for the PDN connection forwhich the UE has allocated the IPv4 address, as described in FIG. 7.

In step 2, the UE requests an IPv4 address. That is, the UE initiates aDHCP discover procedure to procure an IP address.

In step 3, an SGW includes the PDN connection context with a dummy IPaddress. The SGW sends a PBU to the PDN GW with an indication toallocate an HoA. The PDN GW allocates an IP address and responds backwith an actual IP Address.

In step 4, a DHCP relay in the SGW forwards the DHCP discover messagefrom the UE to the PDN GW.

In step 5, the DHCP offer contains the same IP address as allocated inthe determined PBA. The IP address may be same as the IP addresspreviously allocated to the same UE.

In Step 6, the UE confirms the IP address received from the DHCP serverin PDN GW by transmitting DHCP Request for the allocated IP address. TheDHCP transaction is complete by the DHCP Server Acknowledging the DHCPrequest.

In accordance with an embodiment of the present invention, the SGWforwards the DHCP request to PDN GW. The PDN GW can allocate a new IPaddress and send the new IP address message to the SGW. Alternatively,in accordance with another embodiment of the present invention, the SGWcan interpret the DHCP relay message for obtaining an IP addressallocated to the UE and can adjust the BUL according to the allocated IPaddress.

In accordance with an embodiment of the present invention, the PDNconnection is kept active, after the UE requests release of the IPaddress by keeping a dummy DHCP server, by keeping the IP address activealong with the tunnel. The dummy DHCP server is associated with the PDNGW. The associated dummy DHCP server may not allocate resources. Rather,the dummy DHCP server replies with the IP address indicated by the PDNGW. The PDN GW can manage the PDN GW IP addresses or can contact anindependent DHCP server to get allocation of IP addresses for aplurality of UEs. Thus, the processing of the IP address release requestby the associated DHCP server does not release the IP address for use byother UEs.

If the UE is connected to a PDN connection with IPv4 or IPv6 addressesbeing allocated, and the DHCP release procedure releases the IPv4address, the BCE in an LMA and BUL in an MAG are updated to remove theIPv4 address.

To remove the IPv4 address, the LMA sends a binding revocation messageto the MAG. The binding revocation message includes an indication thatonly the IPv4 address is to be revoked. This revoking of the IPv4address is made by including a separate indicator in a BRI or byexcluding the IPv6 Home Network Prefix (HNP) in the BRI.

FIG. 9 is a flow diagram illustrating a method for deleting a PDNinitiated IP version 4 address, in accordance with an embodiment of thepresent invention.

In the step 1, a PDN connection is active for the UE and the UE isallocated with IPv4 and IPv6 addresses. The UE uses a DHCP for obtainingthe IP address and possibly for configuring one or more IP parameters.

In step 2, the UE makes a decision for releasing the IP address andsends a DHCP release message to the SGW, which is relayed by the SGW tothe DHCP server associated with PDN GW.

In step 3, the DHCP server triggers a BRI for the IPv4 address only. TheSGW releases the IPv4 address and can trigger the release of resourcescorresponding to IPv4 address. The SGW acknowledges the BRI with a BRA.

In accordance with an embodiment of the present invention, the IPv4address can be removed after receiving the DHCP release message from theUE, and the SGW can initiate the PBU with lifetime zero so as toderegister the binding with an indication of releasing the IPv4 address.The releasing of the IPv4 can be done by including the IPv4 address inthe PBU or by including a special indicator in the PBU.

FIG. 10 is as flow diagram illustrating a method for deleting a SGWinitiated IP version 4 address, in accordance with an embodiment of thepresent invention.

In step 1, a PDN connection is active for the UE and the UE is allocatedwith IPv4 and IPv6 addresses. The UE uses a DHCP to obtain the IPaddress for configuring one or more IP parameters.

In step 2, the UE makes a decision to release the IP address and sendsthe DHCP release message to the SGW.

In step 3, the DHCP relay triggers a PBU (lifetime=0) with an indicationtriggering the PBU for IPv4 address.

In accordance with an embodiment of the present invention, the PBU mayinclude only an IPv4 address indicating to the LMA the request is forIPv4 address. The PDN GW releases the IPv4 address and acknowledges thePBU, using a PBA.

In Step 4, the DHCP request from the UE is relayed to the DHCP serverassociated with PDN GW. The IPv4 address allocated for the UE isreleased. Upon receipt of the IPv4 delete message from Binding UpdateList (BUL), the SGW can initiate an “update bearer” message for updatinga Service GPRS Support Node (SGSN) of the latest IP addresses in use.

In the preceding specification, the present disclosure and itsadvantages have been described with reference to specific embodiments.However, it will be apparent to a person of ordinary skill in the artthat various modifications and changes can be made, without departingfrom the spirit and scope of the present disclosure, as set forth in theclaims below. Accordingly, the specification and figures are to beregarded as illustrative examples of the present disclosure, rather thanin restrictive sense. All such possible modifications are intended to beincluded within the scope of present disclosure.

1. A method for releasing an Internet Protocol (IP) address using aDynamic Host Configuration Protocol (DHCP) release in a third GenerationPartnership Project (3GPP) Evolved Packet Core (EPC), the methodcomprising: transmitting a DHCP release request from a Serving GateWay(SGW) to a Packet Data Network GateWay (PDN GW); transmitting a bindingrevocation or a PDN disconnection message from the PDN GW to the SGW;acknowledging a binding revocation or PDN disconnection message from theserving gateway to the packet data network gateway; and deleting an IPv4connection for an active PDN connection.
 2. The method of claim 1,further comprising: initiating a PDN disconnection procedure by the PDNGW in order to delete the PDN connection.
 3. The method of claim 1wherein, transmitting the binding revocation comprises: allocating adummy IP address.
 4. The method of claim 1, wherein transmitting thebinding revocation comprises: providing an indication specific to theIPv4 to be deleted.
 5. The method of claim 1, wherein deleting the Ipv4connection, comprises: removing an actual IP address; and updating adummy IP address from the PDN GW to the SGW.
 6. A method forre-allocating an Internet Protocol version 4 (IPv4) address using aDynamic Host Configuration Protocol (DHCP) version 4 request, after anIP address is deleted by the DHCP release, the method comprising:sending an IP address update request from a Serving GateWay (SGW) to aPacket Data Network GateWay (PDN GW); receiving, by the SGW, an actualIP address acknowledgement from the PDN GW; and re-attaching the actualIP address by the SGW.
 7. The method of claim 4, further comprising:deleting a Proxy Mobile Internet Protocol version 6 (PMIPv6) tunnelbetween the SGW and the PDN GW; and updating the PMIP tunnel between theSGW and the PDN GW, when a user equipment requests an IP version 4address for a PDN connection.
 8. A system for deleting a Dynamic HostConfiguration Protocol (DHCP) release in Proxy Mobile Internet Protocolversion 6 (PMIPv6)of a third Generation Partnership Project (3GPP)Evolved Packet Core (EPC), the system comprising: a Serving GateWay(SGW); a Packet Data Network GateWay (PDN GW); a link between the SGWand a User Equipment (UE) for transmitting a DHCP release request; aPMIPv6 or General Packet Radio Service (GPRS) Tunneling Protocol (GTP)between the SGW and a PDN GW server; and a tunneled link between the SGWand the PDN GW for transmitting the DHCP release request, wherein theserving gateway includes a DHCP relay for relaying the DHCP releaserequest between the SGW and a PMIPv6 Mobile Access Gateway (MAG),wherein the PDN GW includes the DHCP server, and wherein the PDN GWincludes a local mobility anchor to revoke a binding for the UE.